Pyrroles and related compounds. Part XXIX. Vinylporphyrin β-keto-esters

Abstract

The first total synthesis of 2,4-divinylrhodoporphyrin-XV dimethyl ester (2c)(via the b-oxobilane route) is reported. General methods for the synthesis of porphyrin β-keto-esters (1) from various rhodoporphyrins by way of the corresponding mixed anhydrides or imidazolides are presented. These are shown to be more efficient than the previous approach via porphyrin acid chlorides and sodiomalonic esters. The synthesis and properties of the β-keto-esters from 2-vinyl- and 2,4-divinyl-rhodoporphyrin-XV dimethyl esters are reported; such compounds may be of significance in chlorophyll biosynthesis.